queryx: added Get, GetRelease, Select and SelectRelease helper functions

I have piggy backed with this change some docs update.

Fixes #41

queryx.go

@@ -191,9 +191,49 @@ func (q *Queryx) Exec() error {
 	return q.Query.Exec()
 }
 
-// ExecRelease performs exec and releases the query, a released query cannot be
+// ExecRelease calls Exec and releases the query, a released query cannot be
 // reused.
 func (q *Queryx) ExecRelease() error {
 	defer q.Release()
 	return q.Exec()
 }
+
+// Get scans first row into a destination. If the destination type is a struct
+// pointer, then Iter.StructScan will be used. If the destination is some
+// other type, then the row must only have one column which can scan into that
+// type.
+//
+// If no rows were selected, ErrNotFound is returned.
+func (q *Queryx) Get(dest interface{}) error {
+	if q.err != nil {
+		return q.err
+	}
+	return Iter(q.Query).Get(dest)
+}
+
+// GetRelease calls Get and releases the query, a released query cannot be
+// reused.
+func (q *Queryx) GetRelease(dest interface{}) error {
+	defer q.Release()
+	return q.Get(dest)
+}
+
+// Select scans all rows into a destination, which must be a pointer to slice
+// of any type. If the destination slice type is a struct, then Iter.StructScan
+// will be used on each row. If the destination is some other type, then each
+// row must only have one column which can scan into that type.
+//
+// If no rows were selected, ErrNotFound is NOT returned.
+func (q *Queryx) Select(dest interface{}) error {
+	if q.err != nil {
+		return q.err
+	}
+	return Iter(q.Query).Select(dest)
+}
+
+// SelectRelease calls Select and releases the query, a released query cannot be
+// reused.
+func (q *Queryx) SelectRelease(dest interface{}) error {
+	defer q.Release()
+	return q.Select(dest)
+}